From your pal Mr Fenner at
wetwebmedia.com,
"All Cleaner Shrimp species prefer subdued lighting, plenty of rocky cover, nooks and crannies..."
Also notice that their cleaning stations or favourite hangouts are places where fish present themselves occasionally for a going-over, and are fairly vulnerable while in this position. It makes sense to be discreet...
Like when the masseuse sets up her table in your living room, and you draw the blinds for privacy.
